Sounds like a good reason to house-rule this metamagic, and maybe push to get it errata'd to better fit the intended flavor.
How about, instead of astral hazing, an Astral Perception check (opposed by Skin Walker's Magic + Initiation, or Threshold of Initiation, I don't know, play with it, see what works) to notice the "bad juju", but not specifically the cause of it. As written, this is part of what assensing is for (spotting things that are metaphysically "wrong"), and it fits with the intention of Skin Walker (sneaky, with a hint of wrong-ness because you just consumed someone, killed them, and bathed in their blood) a lot better than the Astral Hazing does.
Of course, it might be that idea behind the Astral Hazing was to encourage / force the Skin Walker to avoid confrontation (his own magic being so thoroughly hindered) or drop his disguise if he wanted to get seriously violent. But, then again, he can't optionally drop it by a strict reading of the power.
But, there are still better ways to get a +5 bonus on your disguise checks than ritual murder, the real advantage of this metamagic is the mimicked aura (by my reading, much better than what you can do with Masking), and Astral Hazing really puts a damper on that, regardless of how you rule Astral Perception of it (automatically detected / detected if perceived / automatically detected when entered).